Experimental autoimmune encephalomyelitis is an inflammatory demyelinating disease of the central nervous system (CNS) studied as a model of multiple sclerosis. Mice which harbor a monoclonal myelin basic protein (MBP)-specific ab T cell compartment develop EAE spontaneously. EAE can be prevented in these mice by the administration of a small number of polyclonal CD4+ T cells (regulatory T cells or T-reg) belonging to either the CD4+CD25+ or the CD4+CD25- T cell subpopulations. The biological impact of T-reg administration is large, and, therefore, so is its potential for clinical application, yet many important properties of T-reg cells that control spontaneous EAE remain poorly understood. This application focuses on key events involved in immunoregulation of spontaneous EAE in MBP-specific T cell receptor transgenic mice. In Aim 1, we will assess the role of the cytokines, cytokine receptors and co-stimulatory molecules IL-2, CD25, IL-10, TGF-b and CD28 in the generation, survival and function of T-reg. A better knowledge of T-reg dependence on these cytokines and co-stimulatory signals may enhance the potential of in vivo manipulation of immunoregulatory T cells. In Aim 2, we will investigate the MHC restriction of regulatory T cells. The characteristics of MHC restriction of T-reg cells may help in the design of strategies to purify these cells out of the total CD4+ T cell compartment.